Phase shifts in multilayer dielectric beam splitters

Some properties of the reflectivity and transmissivity of multilayer dielec tric optical coatings are derived from energy conservation applied to a bea m splitter acting as a beam combiner. It is shown that dispersion in the ph ase shifts of the beam splitter coatings influences which quadrature amplit ude is measured in a homodyne detector, and, in a Michelson interferometer, how the white-light fringe pattern is disposed about the zero-path-differe nce condition. The functions of reflectivity and transmissivity that determ ine these properties are shown to be not completely constrained by consider ations of energy conservation and time reversibility, in contrast to common ly employed models for beam splitter reflectivity and transmissivity. Some representative beam splitter coating designs are used to illustrate this po int. (C) 2000 American Association of Physics Teachers.